Brake fluid



United States Patent 3,347,796 BRAKE FLUID George L. Doelling, St. Louis, Mo., Joseph A. Siefker, Quincy, Ill., and Edward J. Schwoegler, Munster, and Richard E. Putscher, Hammond, Ind, assignors, by mesne assignments, to Tang-Sol Electric Inc., Newark, N .J., a corporation of Delaware No Drawing. Filed Oct. 27, 1964, Ser. No. 406,909

8 Claims. (Cl. 252-75) This is a continuation-in-part of co-pending application Ser. No. 222,953 (now abandoned), filed September 11, 1962 for brake fluid, which in turn is a continuation-inpart of application Ser. No. 827,455 (now abandoned), filed July 16, 1959, for brake fluid.

This invention relates to hydraulic fluids of the nonmineral oil type. More specifically, it relates to hydraulic brake fluids which are used in automotive vehicles, such as automobiles, trucks and buses.

The invention particularly relates to improved brake fluid compositions including a synergistic combination of effective amounts of compounds which imparts not only superior anti-oxidant properties but also superior anticorrosive properties against copper bearing metals thereto.

In the past, the specification tests for testing brake fluid for corrosion of metals were usually run in sealed containers, not open to the air. The Society of Automotive Engineers Specification 70RI specifies that this test be run in a sealed jar. However, the recently issued Federal Specification VV-H-910 specifies that this corrosion test be run in a vented jar, having a inch hole drilled in the top. This lets a certain amount of air into the top of the jar above the fluid during the test, and as a result, the copper and brass strips in this test are ailected much more than in a sealed or closed corrosion test. The brass and copper strips suffer more loss in weight and are discolored much more in this vented test, than in the sealed or closed test. This VV-H-9l0 specification requires that six (6) metal strips, tinned iron, steel, aluminum alloy, cast iron, brass and copper, together with a rubber cup be heated in 95 parts by volume of the brake fluid under test, plus parts by volume of water, for 120 hours at 210 F., in a vented jar. The copper and brass strips must not lose more than 0.5 mg. per sq. cm. during this test, and the brass must not have more than a slight discoloration, and the copper not more than a moderate discoloration after the test. Many commercial brake fluids, which contain an anticorrosive ingredient, and in some instances an anti-oxidant ingredient, do not pass this test.

An object of the present invention is to provide a brake fluid composition having anti-corrosive properties and anti-oxidant properties which pass or exceed the -minimum requirements of the vented type of corrosion test according to Federal Specification VV-H-910.

Another object of the present invention is to provide a brake fluid composition incorporating therein a synergistic combination of eflective amounts of components which provide not only superior anti-oxidant properties but also superior corrosion inhibiting properties against copper bearing metals as well as ferrous and aluminum bearing metals in the vented type of corrosion test.

And yet another object of the present invention is to provide a novel brake fluid composition which serves not only to reduce the weight loss of copper bearing metals but also serves to substantially reduce discoloration or tarnishing (i.e. for color rating) of said copper bearing metal in a vented type of corrosion test.

These and other objects and advantages will become apparent hereinafter.

3,347,796 Patented Oct. 17, 1967 Briefly, oil type brake fluid composition having incorporated therein a synergistic combination of elfective amounts of potassium ricinoleate and a compound selected from the 5 group consisting of p,p'-tetra methyl diamino diphenyl methane, p,p-benzylidene bis (N,N-dimethyl aniline) and p,p-[p-hydroxy benzylidene bis (N,N-dimethyl aniline)], this combination of compounds providing superior anti-oxidant characteristics and superior corrosion inhibiting characteristics.

This synergistic combination of compounds includes small but effective amounts of potassium ricinoleate in the range from about .4% to 2% based on the weight of the brake fluid.

When p,p'-tetra methyl diamino diphenyl methane is used, from about 0.05% to about 2% by weight of the compound can be used about 0.1% to about 1% the brake fluid.

When p,p'-benzylidene bis (N,N-dimethyl aniline) and p,p-[p-hydroXy-benzylidene bis (N,N-dimethyl ani1ine)] are used, from about 0.05% to about 2% by Weight based on the Weight of the brake fluid can be used, and it is preferred to use from about 0.1% to about 1% of this compound to effect good results.

The following examples further illustrate the present invention.

by Weight based on the Weight of Example N0. 1

Brake Fluid A plus (per 100 cc.) .3 g. Tetra Methyl Diamino Diphenyl Methane, .05 g. Trimethyl Di Hydro Quinoline Polymer Brade Fluid A Tinned Iron- 0 (not stained) 0 (not stained). Steel do Do.

Do. +0.01 (not stained). 0.10 (very slight stain). 0.05 (very slight stain).

do 0.285 (heavy stain) 0.19 (slight to moderate stain). pH, after test 7.53

Brake Fluid A passed the u-nvented test, but does not pass this vented type of corrosion test; but Brake Fluid A, including the aforementioned synergistic combination, does pass the vented type of corrosion test. The brass and copper in the latter case have only a very slight stain which, in this example, illustrates the anti-corrosive properties of tetra methyl diamino diphenyl methane against copper bearing metals imparted to the composition of Brake Fluid A.

Example N0. 2

A with no additive used.

the present invention comprises a non-mineral and it is preferred to use from by weight Color Rating of Weight Loss of Inhibitor, Strips Strips, Mg./ Sq.

Weight Inhibitor 0111. P ercent Brass Copper Brass Copper Di-2-ethyl hexyl amine 4 4 0. 45 0. Tributylamine 3 3 0. 38 -0. Cyelo hexylamino-2-propanol 1 3 0. 75 0. 64 Tetra methyl diamino diphenyl l 2 0. 19 -O. 15

methane. do 0 1 0.l8 -0. 12 do 0 1 +0.08 0.08

When the vented type of corrosion tests are run on each of these two brake fluids the results are as follows:

Brake Fluid Appearance of Strips After Test Weight Lossof Strips Mg./Square Cm.

Brass Copper Brass Copper Brake Fluid 0 Heavy stain and etched- Heavy stain and etched. -0. 64 0. 43 Brake Fluid C, plus additives..." Slight stain Slight stain 0. 266 0. 17

and a moderate discoloration on copper, and such tests, in this example, illustrate not only the anti-corrosive Example N0. 3

Brake Fluid B is another commercial brake fluid of the castor-oil type which normally passed the prior unvented test of the Federal Specification. It contains 0.7 gram of potassium ricinoleate per 100 cc. of brake fluid. In repeated tests using the vented type of corrosion test according to Federal Specification VV-H-910, the brass strip invariably has a heavy stain and the copper strip also is stained considerably. When 0.3 gram of tetra methyl diamino diphenyl methane and 0.05 gram of tri- 5 methyl di hydro quinoline polymer are added, per 100 cc. of Brake Fluid B, the brass has only a very slight stain and a loss of only 0.11 mg. per sq. cm., and the copper has only a very slight stain and a loss of only 0.065 mg. per sq. cm. This result is within the VVH910 Federal Specification test requirements; and in addition, such results further illustrate that the brake fluid including the aforementioned synergistic combination has not only superior anti-oxidant properties but also superior anti-corrosive properties against copper bearing metals.

Example N0. 4 Brake Fluid C is another type of commercial brake fluid which normally passed the prior unvented test of the Federal Specification having a composition approximately as follows:

Brake Fluid C:

adding to each 100 cc. of Brake Fluid C the following additives:

Gram Tetra methyl diamino diphenyl methane 0.2 Trimethyl di hydro quinoline polymer 0.05

The Brake Fuid C (without the additive materials) has a heavy stain and etching on the brass strip, and the Weight loss is over the specification maximum of 0.50 mg. per sq. cm.; therefore said Brake Fluid C does not pass the vented type of corrosion test. After addition of the additive materials, the weight TOsses and appearance of the brass and copper strips are within the specification limits, and the Brake Fluid C (with the additive materials) passes the vented type of corrosion test. The tin, aluminum, steel and cast iron strips in both of these tests are not stained, and suiter practically no loss in weight during these tests.

Example No. 5

Brake Fluid A plus (per cc.) 0.39 g. p,p-benzylidene bis (N,N-dimethyl aniline) Brake Fluid A Tinned Iron... 0 (not stained) +0.01 (not stained). Ste do el 0 (not stained). Alurn1nurn .(lo.-. +0.01 (not stained). Cast Irondo +0.02 (not stained). Brass. -0.285 (heavy stain) -0.09 (very slight stain). Copper -0%19 (s l1ght to moderate -0.05 (very slight stain).

s am. pH, after test 7.53 7.60.

Original Brake Fluid A does not pass this test since the brass has a heavy stain, but Brake Fluid A including the aforementioned synergistic combination does pass this test since the brass and copper have only a very slight stain. Further, it produced very low weight losses. The results of the tests in this example illustrate that the improved brake fluid not only has superior anti-oxidant properties but also superior anti-corrosive properties which efiected reduced weight losses in the copper bearing metals and effected reduced discoloration or tarnishing of said copper bearing metals. In other words, original Brake Fluid A does not pass the vented type corrosion test according to Federal Specification VV-H910, but the improved brake fluid does pass said Federal Specification VV-H-910.

, Example No. 6

Brake Fluid A plus (per droxy benzylidene bis (N, N-dimethyl aniline)] Brake Fluid A.

erate stain).

pH, after test.. 7 53 7.55.

Original Brake Fluid A does not pass this test, but Brake Fluid A including the aforementioned synergistic combination does pass this test. The brass and copper subjected to the improved brake fluid in this example have practically no strain after the test, and the weight losses thereof are low. The results of the tests in this example illustrate that the improved brake fluid has not only superior anti-oxidant properties but also superior anticorrosive properties which serve to reduce the weight loss in copper bearing metals and to reduce discoloration or tarnishing of such copper bearing metals. Further, th improved brake fluid has a very deep red color, which appears to be stable; therefore, p,p'-[p-hydroxy benzylidene bis (N,N-dimethyl aniline)] may also b employed as a coloring agent in the event a red colored composition is desirable.

Example No. 7

' As shown in Example No. 3, when Brake Fluid B is tested by the vented type of corrosion test according to Federal Specification VVH910, the brass strip invariably has a rather heavy stain, and the copper strip also is stained considerably.

When 0.39 gram of p,p-benzylidene bis (N,N-dimethyl aniline) are added, per 100 cc. of Brake Fluid B, and the vented type of corrosion test is run on it, the brass has only a very slight stain and has lost only 0.11 milligram per sq. cm., and the copper has only a very slight stain and has lost only 0.065 milligram per sq. cm. The results of the test in this example illustrate that the improved brake fluid has not only superior anti-oxidant properties but also anti-corrosive properties which serve to reduce weight loss of copper bearing metals and discoloration or tarnishing of such copper bearing metals. This test result is within the Federal Specification VV-H-910 requirements.

Example N0. 8

Brake Fluid B is tested after adding 0.41 gram of p,p'-[p-hydroxy benzylidene bis (N,N-dimethyl aniline)] per 100 cc. of Brake Fluid B. The vented type of corrosion test run on this fluid also gives a satisfactory test result. The brass has only a very slight stain and has lost 0.14 milligram per sq. cm., and the copper has only a very slight stain and has lost only 0.08 milligram per sq. cm.

The results of the test in this example illustrate that the improved brake fluid has not only superior antioxidant properties but also superior anti-corrosive properties which serve to reduce weight loss of copper bearing metals and to reduce discoloration or tarnishing of such copper bearing metals.

From the foregoing, it is apparent that a compound, selected from the group consisting of tetra methyl diamino diphenyl methane, p,p'-benzylidene bis (N,N-dimethyl aniline) and p,p'-[p-hydroxy benzylidene bis (N,N-dimethyl aniline)] and added to the preferred brake fluid composition in amounts between about 0.05% and 2% by weight based on the weight of said brake fluid composition in synergistic combination with from about .4%

to about 2% by weight of potassium ricinoleate affords said brake fluid superior anti-oxidant properties and superior anti-corrosive properties against copper bearing metals in the vented type of corrosion test according to Federal Specification VV-H-910. In addition, the preferred brake fluid composition includes from 5% to 20% by volume of a ricinoleate of glycol, said glycol being an aliphatic glycol having not over five carbon atoms per molecule, from 5% to 20% by volume of a water-insoluble polypropylene glycol having an average molecular weight from 1,000 to 3,000 from 50% to 75% by volume of at least one diluent chosen from the group consisting of methoxy-butanol, a higher alcohol, and the lower (C -C mono-alkyl ethers of diethylene glycol, from 5% to 25% by volume of at least one glycol chosen from the group consisting of propylene glycol, butylene glycol and hexylene glycol.

In addition to the above, it is also apparent that the novel aforementioned synergistic combination can be employed with many of the brake fluids now commercially available and can impart the above-described anti-oxidant and anti-corrosive properties thereto. The commercially available brake fluids generally contain, per parts by weight, at least 20 parts of a water-insoluble lubricant, such as a mixture of a ricinoleate of an aliphatic glycol and a water-insoluble polypropylene glycol having an average molecular weight of 1,000 to 3,000, a diluent selected from the group consisting of methoxybutanol, a higher alcohol, and the lower (C -C mono-alkyl ethers of diethylene glycol, a relatively smaller amount of one or more glycols, such as propylene, butylene or hexylene glycol. An anti-oxidant or anti-corrosion'inhibitor may be or may not be incorporated in the above-described commercially available brake fluid.

The following tests were run on a Fluid C stock solution which is the same as the Brake Fluid C defined in Example No. 4 minus the 1.3 grams per 100 cc. of potassium ricinoleate.

In test No. 1, the Fluid C stock solution has added thereto the synergistic combination of the present invention including potassium ricinoleate and tetramethyl di amino diphenylmethane.

In test No. 2, the stock solution ricinoleate added thereto.

In test No. 3, the stock solution has only tetramethyl diamino diphenylmethane added thereto.

In test No. 4, nothing has been added to the stock solution.

It will be apparent from an inspection of the results of these four tests that the synergistic combination of the potassium ricinoleate and the tetramethyl diamino diphenylmethane provides very superior and unexpected results as compared with those tests where either potassium ricinoleate is added or where the tetramethyl diamino diphenylmethane is added individually, or wherenothing is added to the stock solution.

It is accordingly apparent that the potassium ricinoleate and tetramethyl diamino diphenylmethane provide a true synergistic effect in providing anti-corrosive characteristics to the brake fluid.

has only potassium VENTED CORROSION TESTS ON FLUID C STOCK SOLUTION PLUS ADDIIIVES 1. Brake Fluid 0 Stock Solution Plus 1.3 g. potassium ricinoleate, 0.4 g. tetramethyl diamino diphenyl- 2. Brake Fluid C Stock Solution Plus 1.3 g. potassium ricinoleate per 100 cc. fluid; nothing else added This test does not pass VV-H-910 Spec. Test.

3. Brake Fluid C Stock Solution Plus 0.4 g. tetramethyl diarnino diphenylmethane per 100 cc. of fluid; nothing else added Change in Metal eight, Condition of strip, aiter test Mg./sq. cm.

Tin Slight stain only. Steel 042 Heavy stain and slight pitting. Aluminum. 023 Some pitting over whole surface. Cast Iron- 108 Heavy stain and much pitting. Brass 122 Dark stain near upper end. Copper. -.070 Do.

This test does not pass VV-Il-QlO Spec. Test.

4. Brake Fluid C Stock Solution As is; nothing added Change in Metal Weight, Condition of strip, after test Mg./sq. cm.

Tin 0 No stain. OK.

Steel 140 Heavy stain and pitting.

Aluminum. O89 Pitted over entire surface.

Cast Iron... .276 Heavy stain and corrosion over about of surface. Brass -.136 Hgavg stain over most of surface, very ar Copper. 093 Very dark, heavy stain.

This test does not pass VV-H-QlO Spec. Test.

This invention is intended to cover all changes and modifications of the examples of the invention herein chosen for purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

1. A non-petroleum base hydraulic brake fluid, having superior anti-corrosive properties in a vented type of corrosion test, consisting essentially of, per 100 parts by weight, at least 20 parts of a lubricant, consisting of a ricinoleate of a lower aliphatic glycol, and a polypropylene glycol having a molecular weight of 1000 to 3000, from 50-75 parts of at least one diluent selected from the group consisting of methoxybutanol, N-butanol, and the lower (C to C mono-alkyl ethers of diethylene glycol, from 5-25 parts of a glycol chosen from the group consisting of propylene glycol, butylene glycol and hexylene glycol, together with from about .4% to about 2% by weight of potassium ricinoleate, and from about 0.05% to about 2% by weight of a compound selected from the group consisting of tetramethyl diarnino diphenylmethane, p,p-benzylidene bis (N,N-dimethyl aniline), and p,-p'-[p-hydroxy benzylidene bis (N,N-dimethyl aniline)].

2. The non-petroleum base fluid according to claim 1 wherein said compound is tetramethyl diarnino diphenyl methane.

3. The non-petroleum base fluid according to claim 1 wherein said compound is p,p-benzylidene bis (N,N-dimethyl aniline).

4. The non-petroleum base fluid according to claim 1 wherein said compound is p,p-[p-hydroxy benzylidene bis (N,N-dimethyl aniline)].

5. A non-petroleum base hydraulic brake fluid, having superior anti-corrosive properties in a vented type of corrosion test, consisting essentially of, per 100 parts by volume, from 5% to 20% by volume of a ricinoleate of a glycol, said glycol being an aliphatic glycol having not over five carbon atoms per molecule, from 5% to 20% by volume of a water-insoluble polypropylene glycol having an average molecule weight from 1000 to 3000, from 50% to by volume of at least one diluent chosen from the group consisting of methoxy butanol, N-butanol, and the lower (C to C mono alkyl ethers of diethylene glycol, from 5% to 25% by volume of at least one glycol chosen from the group consisting of propylene glycol, butylene glycol and hexylene glycol, together with from about .4% to about 2% by weight of the fluid of potassium ricinoleate, and from about 0.1% to about 1% by weight of the fluid of a compound selected from the group consisting of tetramethyl diarnino diphenyl methane, p,p-benzylidene bis (N,N-dimethyl aniline), and p,p'-[p-hydroxy benzylidene bis (N,N-dimethyl aniline)].

6. The non-petroleum base fluid according to claim 5 wherein said compound is tetramethyl diarnino diphenyl methane.

7. The non-petroleum base fluid according to claim 5 wherein said compound is p,p'-benzylidene bis (N,N-dimethyl aniline).

8. The non-petroleum base fluid according to claim 5 wherein said compound is p,p-[p-hydroxy benzylidene bis (N'N-dimethyl aniline)].

References Cited UNITED STATES PATENTS 2,722,518 11/1955 Watson 252-78 X 2,803,605 8/1957 Doelling et al. 252-79 2,921,906 1/1960 Doelling et al. 25279 2,290,860 7/1942 Burk et al. 252--49 LEON D. ROSDOL, Primary Examiner.

S. D. SCHWARTZ, Assistant Examiner. 

1. A NON-PETROLEUM BASE HYDRAULIC BRAKE FLUID, HAVING SUPERIOR ANTI-CORROSIVE PROPERTIES IN A VENTED TYPE OF CORROSION TEST, CONSISTING ESSENTIALLY OF, PER 100 PARTS BY WEIGHT, AT LEAST 20 PARTS OF A LUBRICANT, CONSISTING OF A RICHINOLEATE OF A LOWER ALIPHATIC GLYCOL, AND A POLYPROPYLENE GLYCOL HAVING A MOLECULAR WEIGHT OF 1000 TO 3000, FROM 50-75 PARTS OF AT LEAST ONE DILUENT SELECTED FROM THE GROUP CONSISTING OF METHOXYBUTANOL, N-BUTANOL, AND THE LOWER (C1 TO C4) MONO-ALKYL ESTERS OF DIETHYLENE GLYCOL, FROM 5-25 PARTS OF A GLYCOL CHOSEN FROM THE GROUP CONSISTING OF PROPYLENE GLYCOL, BUTYLENE GLYCOL AND HEXYLENE GLYCOL, TOGETHER WITH FROM ABOUT .4% TO ABOUT 2% BY WEIGHT OF POTASSIUM RICINOLEATE, AND FROM ABOUT 0.05% TO ABOUT 2% BY WEIGHT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF TETRAMETHYL DIAMINO DIPHENYLMETHANE, P,P''-BENZYLIDENE BIS (N,N-DIMETHYL ANILINE), AND P,-P''-(P-HYDROXY BENZYLIDENE BIS (N,N-DIMETHYL ANILINE)). 